Information on domain names and their IP addresses, as well as all the other information distributed via DNS is stored in the memory of name servers as Resource Records (RR).

A name server (also referred to as a DNS server) loads data into its cache in several ways. Authoritative data are read from files on a disk or obtained via a zone transfer query from another authoritative servers. Nonauthoritative data are obtained by the server from other servers as it answers of individual DNS queries. Do not forget for special kind of nonauthoritative data - information about root name servers which are loaded locally from disk file.

If a DNS client needs to obtain information from a DNS, it requests RR from the DNS according to its requirements, i.e., a client can request from a domain server an A type RR with the IP addresses of the particular domain name. A client can be a resolver or a name server that cannot resolve the query on its own.

The structure of RR is prescribed...